The diameter of the opening (4a) is matched to the diameter of the collar (14a, 14b) such that the collar (14a, 14b) clips behind an edge (4b) of the opening (4a) on deformation of the housing (4).

The cables are freed from the checking devices once said cables have been fastened and tightened by varying the dimensions of the groove and the diameter of the clamp and cable.

The diameter of the opening (4a) is matched to the diameter of the collar (14a, 14b) such that the collar (14a, 14b) clips behind an edge (4b) of the opening (4a) on deformation of the housing (4).

The flange has a flat upper surface and an outer diameter larger than that of the body.

Each blind hole (40) comprises a collar (48) having a reduced diameter.

For that purpose, a collar (15) having a larger diameter may be used in particular.

The collar has a first outer diameter in a first position and a second outer diameter, larger than the first outer diameter, in the second position.

The throat (604) can also define a throat depression (611).

The exterior surface of the collet has radial projections (31) or expanded diameter portions for locking with the sleeve.

The sleeve has an annular projection (42) or a reduced diameter portion on the interior surface of the sleeve to correspond to the exterior surface of the collet to provide a secure lock between the collet and sleeve.

Plants and scions whose stem or root collar is below a certain diameter should fall outside the scope.

The diameter of a suitable root collar starts at 0.6 cm;

The diameter of the stop collar (19) is not greater than the thickness of the upper heald shaft rod (10).

Said coupling shoulder (7) comprises a radially inwardly oriented peripheral collar (12) on the front end (11) thereof, the inner diameter (Dki) of said collar being smaller than the outer diameter (Dra) of the tubular body (2).

The collet (160, 162) includes a plurality of axially extending slots (176) that permits the diameter of the collet to be varied.